The present invention relates to a burr removing method and apparatus for removing burrs such as welding burrs and the like which are formed when, for example, billets and the like are subjected to butt welding in the continuous rolling of steel bars and the like.
In conventional steel rolling lines, steel pieces such as billets, blooms and the like are rolled one by one and made to products. Recently, however, Japanese Unexamined Patent Publication Nos. 52-43754, 58-151971, 61-30287 and the like propose a method of subjecting a plurality of steel pieces such as billets and the like, which were extracted from a heating furnace, to flash butt welding and continuously rolling them to prevent the drop of a yield caused by the removal of the crop portions at the leading and trailing ends of the steel pieces and to increase productivity.
When steel pieces are welded to each other by flash butt welding, welding burrs are formed to them at the welded sections thereof by the flash and pressure applied thereto. Since the welding burrs are relatively large, they act as flaws in the rolling operation carried out thereafter. Thus, there is a possibility that a yield is lowered by the flaws, and when the steel pieces are wires and like, there is a possibility that they are broken at the portions of the flaws while they are rolled. Accordingly, the welding burrs must be perfectly removed before the steel pieces are rolled.
Japanese Unexamined Patent Publication Nos. 51-42040, 53-147649, 4-178273 and the like disclose burr removing apparatuses for a flash butt welder. However, any of the burr removing apparatuses proposed by them has a fixed-blade-type burr removing unit assembled therein for cutting welding burrs with a cutter fixed between a welder main body and a steel piece moving car so that the welding burrs can be cut just after a welding operation is finished because the cutting resistance of them is low at the time.
Further, Japanese Unexamined Utility Model Publication Nos. 59-176711, 61-199312 and the like disclose a rotary-blade-type burr removing apparatuses for removing a burr formed at an edge of a steel piece by pressing a rotatable circular cutting edge against the burr.
However, in any of the fixed-type-blade and rotary-blade-type burr removing methods, when a stripe-shaped burr 3 formed across the surface of a steel piece 1 is cut along the burr using a cutter 5 as shown in FIG. 1, a protruding burr 4 is formed at an edge of the steel piece 1 although the cut burr 3 is removed to the outside of the steel piece 1 as a cut chip. Accordingly, a problem of the drop of a yield and the like described above is caused by the protruding burr 4 in the rolling operation carried out thereafter.
An object of the present invention is to provide a burr removing method and apparatus by which no protruding burr is formed at the edge of a steel piece from which a burr is removed.
The above object can be achieved by a burr removing method which comprises the steps of disposing a cutter such that the flank of the cutter is substantially in parallel with the surface of a steel piece on which a burr exists and the angle between the cutting edge of the cutter and the edge of the steel piece which the burr intersects is at least 45xc2x0; and cutting the burr located at the edge of the steel piece by relatively moving the cutter toward the outside of the steel piece along the lengthwise direction of the burr.
When a cutter having a polygonal cutting edge is used as the cutter, the burr can be cut with a plurality of cutting edges, whereby the life of the cutter can be increased.
When a cutter having a circular cutting edge which corresponds to a case in which the number of sides of the polygonal cutting edge is increased infinitely, the burr located at an edge of a steel piece may be cut by disposing the cutter having the circular cutting edge such that the flank of the cutter is substantially in parallel with the surface of the steel piece on which the burr exists and the following formula is satisfied with respect to the burr; and cutting the burr located at the edge of the steel piece by the cutter by relatively moving the cutter toward the outside of the steel piece along the lengthwise direction of the burr;
R/2+W/2 less than xcex94 less than Rxe2x88x92W/2xe2x80x83xe2x80x83(1) 
where, W shows the width of the burr, R shows the radius of the cutter, xcex94 shows the shortest distance from the center of the cutter to the center line of the width of the burr.
When a rotatable cutter having a circular cutting edge is used, a burr can be naturally cut with a different portion of the circular cutting edge without the need of a drive force, whereby the life of the cutter can be increased.
The cutter is moved relatively to a burr along the lengthwise direction of the burr in the methods described above. However, the object of the present invention can be also achieved even if the cutter is moved relatively to the burr perpendicularly to the lengthwise direction of a burr as shown in the following methods.
That is, a burr can be removed without the occurrence of a protruding burr by a burr cutting method which comprises the steps of disposing a cutter such that the flank of the cutter is substantially in parallel with the surface of a steel piece on which the burr exists and the angle between the cutting edge of the cutter and the edge of the steel piece which the burr intersects is at least 90xc2x0; and cutting the burr located at the edge of the steel piece by relatively moving the cutter perpendicularly to the lengthwise direction of the burr.
When a cutter having a polygonal cutting edge is used as the cutter as described above, the life of the cutter can be increased.
Further, when a cutter having a circular cutting edge is used, a burr located at an edge of a steel piece may be cut by disposing the cutter having the circular cutting edge such that the flank of the cutter is substantially in parallel with the surface of the steel piece on which the burr exists and the center of the cutter is located outwardly of the edge of the steel piece which the burr intersects; and cutting the burr located at the edge of the steel piece by relatively moving the cutter perpendicularly to the lengthwise direction of the burr.
When a rotatable cutter having a circular cutting edge is used as the cutter as described above, the life of the cutter can be increased.
The burr removing method of moving a cutter in the lengthwise direction of a burr as the present invention can be realized by a burr removing apparatus which comprises a burr detector; two cutters each having a circular cutting edge; and a drive control mechanism for causing the cutters to approach to a burr in response to a burr detecting signal issued by the burr detector, disposing the cutters so that the following formula (1) are satisfied with respect to the burr and then moving the cutters along the lengthwise direction of the burr, wherein the two cutters are disposed across a steel piece;
R/2+W/2 less than xcex94 less than Rxe2x88x92W/2xe2x80x83xe2x80x83(1) 
where, W shows the width of the burr, R shows the radius of the cutter, xcex94 shows the minimum distance from the center of the cutter to the center line of the width of the burr.
Further, the burr removing method of moving a cutter such that it is perpendicular to the lengthwise direction of a burr can be realized by a burr removing apparatus which comprises a burr detector; a plurality of at least two cutters; and a drive control mechanism for causing the cutters to approach to a burr in response to a burr detecting signal issued by the burr detector, wherein two cutters of the plurality of cutters have a circular cutting edge and the two cutters having the circular cutting edge are disposed such that the centers thereof are separately located outwardly of both the edges of a steel piece which the burr intersects.